The expanded version just added some extra scenes involving characters like "Trashcan man" and "The Kid" that were cut out by the editors when the book was originally published. Some of what was cut (according to Mr. King) deserved to be and wasn't put back in when the expanded version was published. I have both (in paper) and haven't noticed that the expanded version is that much thicker than the cut version.

I didn't particularly care for the *ending* of the expanded one. I don't remember the differences between the other additions...just the ending.

Oh, I don't remember a difference, I read them years apart. Dang, now I have to dig out both my paperback versions and check out the endings. Grumble grumble, can't change font size, eyes too old for the small font in paper backs, grumble grumble....
S